The article is about using OO techniques directly in C code. Lua is implemented in C but it's an entirely separate language. Does its implementation use OO techniques as part of its C source code? If not, then it's not really relevant.
I don't see how a distinction here is anything but semantically arbitrary.
Transitively, it most definitely uses OO techniques. Furthermore, by having such a clean C ffi (in both directions) it allows for the weaving of the Lua based OO techniques back into C code.